Lin-nan-yeh-chu, is the dried entire plant of Vernonia paltula (Compositae) and used as folk medicine in Taiwan. To evaluate the quality of V. paltula, a simple, rapid and accurate high-performance liquid chromatographic (HPLC) method was developed for the assay of four flavonoids apigenin (API), apigenin-7-O-glucoside (APG), luteolin (LUT) and luteolin-7-O-glucoside (LUG). The present HPLC system uses an Inertsil ODS-2 column by gradient elution with acetonitrile and 0.1% (v/v) phosphoric acid as the mobile phase. Ethyl paraben was used as an internal standard and detected at 254 nm. Regression equations revealed good linear relationships (correlation coefficients: 0.9998-0.9999) between the peak-area ratios of each constituent to ethyl paraben. The recovery of four marker constituents ranged from 89.3 to 95.6%. The contents of the four constituents in stem, flower, leaf and root parts of V. paltula have been compared. Leaf part consisted of the highest contents of flavonoids except for APG which is less than that in the flower. The root and stem only showed trace amount of APG but not the other three flavonoids. The contents of four constituents were 0.6016, 0.0042, 0.2160 and 0.0577 mg/g for apigenin-7-O-glucoside, apigenin, luteolin-7-O-glucoside and luteolin, respectively. HPLC chromatograms of another three plants of genus of Vernonia in Taiwan, V. cinerea, V. elliptica and V. gratiosa, have also been compared.